1. Field of the Invention
The present invention relates to an aircraft engine run-up hangar and, more specifically, to an aircraft engine run-up hangar having an improved air inlet structure through which fresh air is taken into a test chamber, an improved current-straightening structure disposed near the air inlet structure, and an improved exhaust structure through which gases are discharged from the test chamber, and capable of producing stable air currents in the test chamber.
2. Description of the Related Art
An overhauled aircraft engine or an aircraft engine of an aircraft to be placed in commission is subjected to a ground run-up in an open space for performance test. Various noise control measures have been taken for environmental protection. Generally, a noise-suppressing duct is disposed just behind the exhaust cone of the engine for outdoor run-up. Some recent run-up method uses a building capable of entirely housing an aircraft therein and having a noise control function, which is called a noise control hangar. Generally, an air inlet structure included in a noise control hangar is incorporated into the front end part of the noise control hangar to take air into the noise control hangar. Such a noise control hangar of a front air inlet type is provided with a big door provided with an inlet structure having current-straightening and noise control functions at its front end. This big door must be opened when carrying an aircraft into or out of the noise control hangar. The air inlet structure having current-straightening and noise control functions is inevitably long and, consequently, the big door provided with the long air inlet structure is inevitably very thick. The thickness of a big door included in a practical noise control hangar of a front inlet type is as big as 7.5 m.
Operations for opening and closing the big door provided with the air inlet structure and having a big thickness to carry an aircraft into or out of the noise control hangar need a large-scale door operating mechanism, and a large operating space is necessary for moving and storing the big door provided with the air inlet structure. Thus, the thick big door and the large operating space increase equipment costs. Moreover, the air inlet structure provides a large intake resistance and hence the back flow of exhaust gas is liable to occur in the noise control hangar. If wind blows outside across a direction in which air flows into the air inlet, it is difficult to produce uniform air currents by straightening air taken in through the air inlet and hence it is difficult to carry out the run-up of the aircraft engine under proper run-up conditions.
A previously proposed noise control hangar is provided with an air inlet in a front end part of the roof structure of the noise control hangar instead of in the front end of the noise control hangar. A noise control hangar proposed in, for example, JP-A 318696/2000 is provided with an air inlet formed in a front end part of the roof structure of the noise control hangar corresponding to the front end part of the noise control hangar, and an exhaust duct to be connected to the exhaust port of an aircraft engine and placed in the test chamber defined by the noise control hangar. Exhaust gas discharged from the aircraft engine is discharged outside through an exhaust line arranged in a back end part of the noise control hangar during the run-up of the aircraft engine. The exhaust duct must be moved every time aircrafts are changed and much labor is necessary for moving the exhaust duct. A noise control hangar disclosed in JP-A 313399/2000 has a roof structure provided with an inlet opening in a front end part thereof corresponding to the front end part of the noise control hangar, and is provided with an exhaust line extending backward and upward from the back end of a test chamber, and circulation-preventive plates having a J-shaped cross section disposed on a part of a ceiling in a back part of the test chamber to prevent the circulation of the exhaust gas.
In the prior art noise control hangar disclosed in JP-A 318696/2000, air currents flowing through the air inlet formed in the roof structure into the test chamber impinge on the floor of the test chamber and then flow backward. Thus, the downward air currents flowing through the air inlet into the test chamber cannot be regularly deflected so as to flow backward toward the aircraft and most part of the air currents is liable to produce eddies and turbulent flows, making it difficult to carry out run-up under proper run-up conditions.
Since the height of the vertical tail fin of an aircraft is greater than that of main wings holding wing engines, the height of the ceiling of a noise control hangar must be greater than that of the vertical tail fin. In such a noise control hangar, the exhaust gas discharged backward from the engine tends to flow forward through an upper region of a space defined by the noise control hangar and hence the exhaust gas is liable to be sucked into the engine, which makes it difficult to carryout the run-up of the engine under proper run-up conditions.
The noise control hangar disclosed in JP-A 313399/2000 has the air inlet formed in the front end part of the roof structure and provided with a current-straightening structure including a plurality of vertical plates longitudinally arranged at predetermined intervals. This noise control hangar has the following problems because any other current-straightening means is not disposed near the air inlet. The upper end of the air inlet is exposed on the roof structure to enable fresh air to flow directly into the air inlet. Under a stormy condition, air is unable to flow uniformly through the air inlet, eddies are liable to be produced in air currents and air currents are liable to be disturbed. Since the current-straightening structure disposed at the air inlet includes the plurality of plates, eddies and turbulence are liable to remain in the air currents below the current-straightening structure.
Accordingly, it is an object of the present invention to provide an aircraft engine run-up hangar including a building defining a test chamber and having a roof structure provided with an air inlet, capable of deflecting air currents flowing through the air inlet into the building toward an aircraft housed in the building and of satisfactorily straightening air currents flowing through the air inlet into the building, and not requiring any exhaust duct in a test chamber defined by the building.
According to the present invention, an aircraft engine run-up hangar includes: a building defining a test chamber capable of receiving an aircraft therein; an air inlet structure; and an exhaust structure; wherein the air inlet structure is formed in a front end part of a roof structure corresponding to a front end part of the building, the exhaust structure is connected to a rear end part of the building and defines an exhaust passage extending obliquely upward from the back end of the building, and one or a plurality of current deflecting members are disposed near a lower end of the air inlet structure to deflect air currents flowing through the air inlet structure into the building toward an aircraft housed in the building.
The air inlet structure is disposed on the roof structure and hence a large door for closing a large opening through which the aircraft is carried into or out of the building does not need to be provided with any air inlet structure, and the large door may be of simple construction similar to that of an ordinary soundproof door. Therefore any space for moving and storing the large door is not necessary, which is favorable to saving space necessary for installing the aircraft engine run-up hangar and is convenient in incorporating various current-straightening means into the air inlet structure. Since the air inlet structure is disposed on the front end part of the roof structure corresponding to the front end part of the building, air currents introduced through the air inlet structure into the test chamber tend to flow vertically downward, to impinge on the floor of the test chamber, to be disturbed and to induce reverse currents in the test chamber. However, the one or the plurality of current deflecting members disposed near the lower end of the air inlet structure deflect the air currents so that the air currents flow substantially horizontally toward the aircraft and do not impinge on the floor of the test chamber. Thus, scarcely disturbed, scarcely swirling stable air currents flow into the engine of the aircraft to ensure proper run-up conditions.
Since the exhaust structure is connected to the rear end part of the building so as to form the exhaust passage extending obliquely upward from the back end of the building, any work for moving an exhaust duct is not necessary when aircrafts are changed. Since air in the test chamber is discharged upward through the back end part of the building, the exhaust structure has a comparatively short length and needs a comparatively small space for installation behind the building, which is favorable to saving space necessary for installing the aircraft engine run-up hangar.
Preferably, the aircraft engine run-up hangar further includes an air-permeable wind guard structure rising from the roof structure of the building and surrounding the air inlet of the air inlet structure. The wind guard structure reduces the effect of wind and wind direction on the air currents flowing through the air inlet structure into the test chamber and makes uniform the distribution of velocities of the air currents in the entire region of the air passage in the air inlet structure.
Preferably, the air inlet structure is provided with a current-straightening structure provided with a plurality of plates arranged in a grid or a honeycomb so as to define vertical current-straightening passages. Thus, the air currents are straightened so as to flow regularly downward. When the plurality of plates arranged in a grid or a honeycomb of the current-straightening structure are formed of a sound-absorbing material, run-up noise emitted by the engine during run-up in the building can be controlled by the current-straightening structure and emission of noise through the air inlet structure of the building can be reduced. Since the current-straightening structure incorporated into the air inlet structure opens upward, the run-up noise diffuses upward into the atmosphere and the level of the run-up noise propagating around the building can be reduced.
Preferably, a first current-straightening member is disposed at the lower end of the current-straightening structure. The first current-straightening member straightens the air currents still further.
Preferably, a current-straightening space of a predetermined height is formed under the current-straightening structure in a region below the current deflecting member or members, and a second current-straightening member is disposed in a lower end part of the current-straightening space. Air currents flowing at different velocities below the plurality of plates of the current-straightening structure can be uniformed and small eddies produced in the air currents can be eliminated in the current-straightening space.
Preferably, a plurality of third current-straightening members are disposed vertically in the current-straightening space so as to extend in the direction of the air currents. The third current-straightening members promote the straightening of the air currents in the current-straightening space.
Preferably, the air inlet structure is disposed at a position on the front end part of the roof structure of the building corresponding to a position in front of the aircraft housed in the building. Thus, the air currents flowing through the air inlet structure into the building can be deflected by the current deflecting member so as to flow in a substantially horizontal direction toward the aircraft.
Preferably, the air inlet of the air inlet structure has a width nearly equal to the width of the front end part of the building. Thus, the air inlet structure has a large sectional area and hence air currents flow through the air inlet structure at low velocities. Consequently, air currents can be effectively straightened and the flow of the air currents in lateral directions in the building can be effectively suppressed.
Preferably, the one or the plurality of current deflecting members are plates having a substantially J-shaped cross section. Therefore, air currents on the back side of the current deflecting member or members are deflected backward by the guiding effect of the current deflecting member or members, and air currents on the front side of the current deflecting member or members are deflected backward by the Coanda effect.
Preferably, the one or the plurality of current deflecting members are plates having a substantially J-shaped cross section, and the current deflecting member or members are disposed in a region around a position at a distance equal to {fraction (3/14)} to {fraction (3/7)} of the length of the air inlet structure from the back end of the air inlet structure. Since an air passage part of a length in the range of about {fraction (3/14)} to {fraction (3/7)} of the length of the air inlet structure opens behind the current deflecting member or members, air currents flow on the front and the back side of the current deflecting member or members, and the current deflecting member or members exercise both the guiding action and the Coanda effect with reliability. The range {fraction (3/14)} to {fraction (3/7)} was determined empirically, which will be described later.
Preferably, a fourth current-straightening member is extended from a position near the lower end of the current deflecting member to a ceiling included in the building on the back side of the current deflecting member. The fourth current-straightening member straightens air currents flowing on the back side of the current deflecting member.
Preferably, the current deflecting member having the substantially J-shaped cross section is provided with one or a plurality of flaps. The flaps suppress the generation of eddies attributable to burble, which is liable to occur on the front side of the curved part of the current deflecting member.
Preferably, the plurality of current deflecting members are formed integrally with lower edge parts of a plurality of plates extended laterally in the current-straightening structure, respectively. The air currents straightened by the current-straightening structure can be effectively deflected.
Preferably, the plurality of current deflecting members comprise a plurality of guide members arranged at predetermined longitudinal intervals. Thus, the air currents straightened by the current-straightening structure can be effectively deflected.
Preferably, the plurality of guide members extend downward such that lower edges of the guide members nearer to the front end of the building are at lower levels. Thus, the deflected air currents will not be easily disturbed and the air currents are stabilized.
Preferably, a vertical tail fin passing gap that permits the vertical tail fin of an aircraft to pass when carrying the aircraft into or out of the building is formed in a middle part of each of the current deflecting members, and the vertical tail fin passing gap is covered with a movable cover. Thus, the covers are moved away from the vertical tail fin passing gaps to open the vertical tail fin passing gaps so that the vertical tail fin is able to pass through the vertical tail fin passing gaps and the aircraft can be carried into or out of the building even if the lower edges of the current deflecting members are at a level below that of the tip of the vertical tail fin. The vertical tail fin passing gaps are closed by covering the same with the covers during run-up to achieve the deflection of air currents without being affected by the vertical tail fin passing gaps.
Preferably, a pair of vertical current-straightening plates are disposed at the opposite ends of the vertical tail fin passing gap of each current deflecting member so as to extend longitudinally. The current-straightening plates reduce the swirling or turbulent flow of air at edges defining the vertical tail fin passing gap of each current deflecting member.
Preferably, the wind guard structure has an open-area ratio in the range of 50% to 75%. Thus, the wind guard structure provides a low resistance against the passage of air currents and exercises a satisfactory protective function against wind.
Preferably, the wind guard structure has a mean height of 2.0 m or above. The wind guard structure exercises a satisfactory protective function against wind.
Preferably, an air-permeable, upper wind guard is disposed on the upper end of the wind guard structure at a level substantially equal to that of the upper end of the wind guard structure so as to cover the upper end of the air inlet structure. The upper wind guard reduces the effect of wind and wind direction on air currents flowing therethrough into the air inlet structure and uniforms the distribution of velocities of the air currents in the entire region of the air passage of the air inlet structure.
Preferably, the current-straightening structure is formed in a predetermined length with respect to the flowing direction of air. Thus, the current-straightening structure has a satisfactory current-straightening ability.
Preferably, the plates of the current-straightening structure are formed of a sound absorbing material. Thus, the current-straightening structure is capable of effectively absorbing run-up noise propagating outside from the building through the air inlet structure for silencing.
Preferably, the first current-straightening member is formed from a metal net, a textile net, a perforated plate, a slit plate or an expanded metal, and has an open-area ratio in the range of 40% to 70%. The first current-straightening member is simple in construction and is capable of exercising a current-straightening ability without exerting an excessive resistance on air currents.
Preferably, the second current-straightening member is formed from a metal net, a textile net, a perforated plate, a slit plate or an expanded metal. The second current-straightening member is simple in construction and is capable of exercising a current-straightening ability without exerting an excessive resistance on air currents.
Preferably, the third current-straightening member is formed from a metal net, a textile net, a perforated plate, a slit plate or an expanded metal. The third current-straightening member is simple in construction and is capable of exercising a current-straightening ability without exerting an excessive resistance on air currents.
Preferably, the fourth current-straightening member is formed from a metal net, a textile net, a perforated plate, a slit plate or an expanded metal. The fourth current-straightening member is simple in construction and is capable of exercising a current-straightening ability without exerting an excessive resistance on air currents.